Tanks for the storage and transport of fluid media under pressure

Abstract

A tank for the transport or storage of liquified natural gas under pressure is of generally rectangular form and has its side, top and bottom walls each composed of a series of parallel lobes of part-spherical cross-section and of say, 3.0 to 4.0 meters chord distance, each tank end consisting of either a like series of lobes or a mosaic of domes. All the inter-lobe nodes of the top wall of the tank are united to the corresponding nodes of the tank bottom by vertical tie-plates; likewise all the corresponding inter-lobe nodes of the two side walls are united by transverse tie-plates which intersect the vertical tie-plates orthogonally, and thereby define with them a plurality of tunnels of square cross-section. The tie-plates extend longitudinally to unite the end walls of the tank and are welded to one another at all tie-plates inter-sections. The tank is supported on a series of parallel support ribs or frames that connect with the tank along the inter-lobe nodes of the tank bottom.

What we claim is: 
     
       1. An internal-pressure-sustaining insulatable tank of generally rectangular cross-section for the storage and transport of fluid media under pressure, comprising a bottom wall, a top wall, two opposite longitudinal side walls and two opposite end walls, an internal framework of plates, bottom supports and top supports; each of said bottom, top and side walls consisting of a multiplicity of equal-sized parallel lobes, each lobe of part-cylindrical form having an arc in the range 50° to 90° and being convex outwardly of the tank with each of its two inwardly-directed longitudinal edges joined to both a longitudinal edge of a lobe alongside and an edge of a plate of said internal framework; each of said end walls consisting of a multiplicity of equal-sized convex end wall elements having the same radius of curvature as said lobes and each joined at its inwardly directed edges to the end wall elements alongside and to plates of said internal framework; tank corner elements being provided to unite said bottom, top, side and end walls to one another, said corner elements being convex and of the same radius of curvature as said lobes but with larger arcs; said internal framework consisting of two orthogonally intersecting series of parallel plates, each plate in one series extending from the joint between two lobes of one side wall to the respective opposite joint of the opposite side wall, each plate in the other series extending from the joint between two lobes of the bottom wall to the respective opposite joint between two lobes of the top wall, and the plates of at least one of said series extending longitudinally and being also united to the joints of the opposite end walls so that the tank end walls are tied to one another longitudinally; the joints at the intersections of the two series of plates being formed by cruciform section insert elements with the end edges of the four arms of the cruciform welded to respective plates, the joints between the bottom wall lobes and plates of the internal framework being formed by bottom insert elements having a crosssection that is generally cruciform with vertical top and bottom arms and downwardly drooped side arms, the side arms being welded to the respective bottom wall lobes and the top arms being welded to the respective internal plates, the joints between the side wall lobes and the plates of the internal framework being formed by Y-section insert elements with the arms thereof welded to the respective side wall lobes and internal plates, and at least some of the joints between the top wall lobes and the plates of the internal framework being formed by top insert elements having a cross section that is generally cruciform with vertical top and bottom arms and upwardly inclined side arms, the side arms being welded to the respective top wall lobes and the bottom arms being welded to the respective plates; and wherein said bottom supports include longitudinally-extending grooves which are located under the tank and slidably engage with the bottom arms of the bottom insert elements to thereby support and permit longitudinal expansion of the tank with space below the lowermost parts of the bottom wall lobes, and said top supports are located above the tank and engage the top arms of the top insert elements. 
     
     
       2. A tank according to claim 1, wherein the tank end walls are composed of square-based domes. 
     
     
       3. A tank according to claim 1, wherein the lobes of the tank longitudinal side walls run longitudinally from one end of the tank to the other so that the tunnels defined by the intersecting tie-plates are horizontal. 
     
     
       4. A tank according to claim 3, wherein the cross-section of the tank is uniform throughout its length and the lobes of the top and bottom walls run longitudinally so that the tunnels defined by the intersecting tie-plates are also longitudinal. 
     
     
       5. A tank according to claim 1, wherein the lobes have arcs of substantially 65°. 
     
     
       6. A tank according to claim 1, wherein the module distance between consecutive inter-lobe joints is in the range 3.0-4.0 meters, especially 3.5 meters. 
     
     
       7. A tank according to claim 1, wherein the principal stress in the tie-plates is higher than the hoop stress in the lobes. 
     
     
       8. A tank according to claim 1, wherein the bottom supports are in the form of upright A-frames located immediately under the joints between adjacent bottom lobes of the tank. 
     
     
       9. A tank according to claim 8, wherein the lobes of the tank top and bottom are longitudinal and the supports extend longitudinally. 
     
     
       10. A tank according to claim 9, installed in a ship, wherein the bottom supports incorporate hydraulic means, to avoid bending loads on the tank when the ship flexes. 
     
     
       11. A tank according to claim 1, wherein the top supports above the tank are connected thereto by joints that allow relative sliding. 
     
     
       12. An internal-pressure-sustaining insulatable tank of generally rectangular cross-section for the storage and transport of fluid media under pressure, comprising a bottom wall, a top wall, two opposite longitudinal side walls and two opposite end walls, an internal framework of plates, bottom supports and top supports; each of said bottom, top and side walls consisting of a multiplicity of equal-sized parallel lobes, each lobe of part-cylindrical form having an arc in the range 50° to 90° and being convex outwardly of the tank with each of its two inwardly-directed longitudinal edges joined to both a longitudinal edge of a lobe alongside and an edge of a plate of said internal framework; each of said end walls consisting of a multiplicity of equal-sized convex end wall elements having the same radius of curvature as said lobes and each joined at its inwardly directed edges to the end wall elements alongside and to plates of said internal framework; tank corner elements being provided to unite said bottom, top, side and end walls to one another, said corner elements being convex and of the same radius of curvature as said lobes; said internal framework consisting of two orthogonally intersecting series of parallel plates, each plate in one series extending from the joint between two lobes of one side wall to the respective opposite joint of the opposite side wall, each plate in the other series extending from the joint between two lobes of the bottom wall to the respective opposite joint between two lobes of the top wall, and the plates of at least one of said series extending longitudinally and being also united to the joints of the opposite end walls so that the tank end walls are tied to one another longitudinally; the joints between the bottom wall lobes and the plates of the internal framework being formed by bottom insert elements with vertical top arms and downwardly drooped side arms, the side arms being welded to the respective bottom wall lobes and the top arms being welded to the respective internal plates, at least one of said bottom insert elements having downwardly projecting key means integral therewith; the joints between the side wall lobes and the plates of the internal framework being formed by Y-section insert elements with the arms thereof welded to the respective side wall lobes and internal plates, and the joints between the top wall lobes and the plates of the internal framework being formed by top insert elements with vertical bottom arms and upwardly inclined side arms, the side arms being welded to the respective top wall lobes and the bottom arms being welded to the respective plates, at least one of said top insert elements having upwardly projecting key means integral therewith; and wherein said bottom supports include longitudinally-extending grooves which are located under the tank and slidably engage with the bottom insert elements to thereby support and permit longitudinal expansion of the tank with space below the lowermost parts of the bottom wall lobes, and said top supports are located above the tank and engage the top insert elements, said key means on said bottom and top insert elements cooperating respectively with said bottom and top supports to restrain bodily movement of the tank.